The invention is related to the field of particle detectors, and in particular to neutron detectors.
It is known that fissile material emits so-called “fast” neutrons, i.e., neutrons with energy in the range of 1 MeV. For security purposes it may be desirable to employ neutron detection in order to detect the presence of fissile material which may pose a security threat. For example, detectors can be placed at points of entry of personnel or cargo, so that attempts to transport fissile material through such a point of entry can be detected and appropriate security measures taken. Neutron detection has also been used for other applications.
A paper of Fraga et al. entitled “CCD Readout of GEM Based Neutron Detectors” describes a gas neutron detector having a chamber with a mixture of carbon tetrafluoride (CF4) and helium, along with so-called gas electron multiplier (GEM) plates which promote scintillation that is detected by a CCD camera. The GEM plates include a large number of small openings in which very high field strengths are maintained, so that ionization electrons entering these openings undergo rapid acceleration and induce scintillation of the CF4 gas.
U.S. Pat. No. 6,627,897 of Francke et al. describes an apparatus for detection of ionizing radiation, wherein the incident radiation ionizes a substance, and the electrons released as a result thereof are accelerated in a dual parallel plate electrode arrangement. These electrons will interact with a scintillating substance to emit light, which is detected by a position sensitive light detector.